Bob wrote:
On the CAT200B manual I have, page 6-2 tells all about adding C10 and/or C11, and the value they supply is 0.0047uF. Don't chastise them so hastily. Engage eyes before shifting fingers!
Well, to each his own, but not listing the value on the schematic is just plain stupid in my book. Obviously Jim thought he had it right, and since the schematic was of no help to me, I found it wasn't that easy. Another gentleman said he had to add a de-emp circuit externally, obviously because he missed it too, so I don't think it's just me....
They probably designed the audio stage to reject sub-audible tones.
The controller shouldn't '/be designed/' to do anything over and above relaying audio that is full bandwidth. The controller should not be a /limiting/ factor, unless done so with intent. If you read the manual, there is nothing that states their audio path is designed to reject sub audible tones, so we must assume it's done without intent.
The audio response is perfectly adequate when driven from a de-emphasized audio source and feeding a transmitter that will follow it with pre-emphasis.
If you feel that an audio response from 300 to 2500 cycles is adequate, then you and I differ on what is adequate.
In my case, using MaxTracs, I just use the constant amplitude Headset Audio available on the front panel RJ45 MIC jack, and feed audio into the MIC input on the same jack. As both of these already have sub-audible audio filtered out, the controller has no problem with the audio.
Right, the RADIO filters the PL, so the controller doesn't need to. Filtering and processing of audio _from basic design limitations_ is bad engineering, in my book.
Using a 0.05uF cap for de-emphasis will likely make it take effect way too early, considering everything else in the system.
Maybe way too early for your liking, but I like an audio chain that is flat from 60 Hz to the upper cut-off of the clipper/filter. Notch filtering of PL tones makes for much better sounding audio, over just loping off everything below xF. The Com-Spec TS-32's HPF is a good example of what /not/ to do in a quality audio chain.
As was mentioned earlier, if the Micor circuitry provides flat audio in and out, it is up to the person doing the controller integration to add the appropriate pre- and de-emphasis.
There are many ways to implement a controller in a MICOR. The point is it should be easy to add de-emphasis to the controller. Look at any other good controller on the market, none that I'm aware of (Link-Comm, S-COM, Arcom, etc.) are that hard to find the information on, or to actually set the controller to de-emphasize the RX.
It's just too bad that CAT doesn't change a few component values so their audio chain isn't bandwidth limited. A much better product, and better sounding repeaters would result. At least other companies out there do care, and either have always had good audio chains (S-COM, Link-Comm) or are receptive to change, like ICS; who has one of the simplest, cleanest, and widest audio paths out there.... Look at their controller for the MICOR, audio wise, it don't get any better.
We constantly talk about quality audio on this list, and what to do to achieve it. Articles have been written to allow greater audio bandwidths to be properly deployed. It just angers me that we go through all of this, and then we see folks that are suffering from 1980's mentality/technology in a recently released product, and don't understand why. This is why........
Kevin Custer
